Open
Description
Summary
Currently, in the latest rust nightly, it's not possible to pass an impl AsyncFn into a function that takes an impl Fn to call it without awaiting, without using a closure as a workaround.
Still, clippy warns about using a closure to do this, and assumes you can just pass the asynchronous function directly, which would give a compile error.
Lint Name
clippy::redundant_closure
Reproducer
I tried this code (within an async context):
pub async fn visit_async<'a, T, const N: usize, F>(array: &'a [T; N], visitor: F)
where
F: AsyncFn(&'a T),
T: 'a
{
//let futures = array.each_ref().map(visitor); // This is what clippy wants me to do, which, i agree, looks nicer, does not actually compile.
#[allow(unused)] // Temporarily because of todo!()
let futures = array.each_ref().map(|x| visitor(x));
// This is where i'd somehow join all the futures in the array `futures` and await them.
// futures.join_all().await // For example, if join_all was a thing
todo!()
}I saw this happen:
$ cargo clippy
Checking minimum_reproducable_example v1.0.5 (/home/sigurd/Code/rust/sss/minimum_reproducable_example)
warning: redundant closure
--> minimum_reproducable_example/src/lib.rs:9:40
|
9 | let futures = array.each_ref().map(|x| visitor(x));
| ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `visitor`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_closure
= note: `#[warn(clippy::redundant_closure)]` on by default
warning: `minimum_reproducable_example` (lib) generated 1 warning (run `cargo clippy --fix --lib -p minimum_reproducable_example` to apply 1 suggestion)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.20s
I expected to see this happen:
No warning, because what clippy suggests to do instead is not possible at the moment.
Version
$ rustc -Vv
rustc 1.85.0-nightly (dd84b7d5e 2024-12-27)
binary: rustc
commit-hash: dd84b7d5eec3c20d7fcd13e6450af029d3cece9d
commit-date: 2024-12-27
host: x86_64-unknown-linux-gnu
release: 1.85.0-nightly
LLVM version: 19.1.6
Additional Labels
@rustbot -I-suggestion-causes-error